Service 4WD light turned on

Hi Bret, often times a faulty wheel speed sensor can cause the light to turn on. Are any other lights on? Have you tried scanning the can-bus system? CAN stands for controller area network. Basically, all the computers and modules are tied together via a few wires. By scanning the "can" it should identify any issues regardless of the module on the vehicle.

Here is a video showing how it's done:

https://youtu.be/InIlnsjOVFA

I would start by doing the scan. If you can't, let's confirm that all wheel speed sensors are working. Here is a link that explains how to do it:

https://www.2carpros.com/articles/abs-wheel-speed-sensor-test

Let me know what you find or if you have other questions.

Take care and God bless.

Joe